Resin composition for controlling interlayer size, prepreg, and structural member, and method for manufacturing structural member

Abstract

The application discloses a resin composition for controlling the thickness of a positive R-angle structure, a prepreg and a preparation method and a structure, and the resin composition comprises: a resin matrix 55.7-72.3%; a first toughening agent 12.7-30.3%; and a second toughening agent 8.2-18.4%; wherein the resin matrix comprises a resin component and a curing agent, the equivalent ratio of active groups in the curing agent to reactive groups in the resin component is 0.70-0.85; the solubility of the first toughening agent in the resin component is greater than or equal to a first preset threshold; the solubility of the second toughening agent in the resin component is less than or equal to a second preset threshold; and the average particle size of the second toughening agent is 15-35 mu m. Through the cooperation of the first toughening agent and the second toughening agent, the application can provide a toughening effect, increase the resistance of the resin component in the positive R-angle area, reduce the sensitivity of the positive R-angle area to high pressure, and thus reduce the thickness of the positive R-angle.

Description

Technical Field

[0001] This application relates to the field of composite material technology, and in particular to a resin composition, prepreg, preparation method and structural component for interlayer dimension control structural component with excessive thickness at the outer R-angle. Background Technology

[0002] Prepregs are widely used in the aerospace industry due to their excellent structural stability and high process reliability. In aircraft, especially manned aircraft, the application of prepregs is gradually increasing. In some current models of civil airliners, the main load-bearing structures such as the fuselage, wings, and tail are all made of prepregs. However, the processing characteristics of prepreg-molded structural components may lead to differences in the thickness dimensions of different structures. When these differences are significant, they can affect the safety of the structural component.

[0003] A typical example is the out-of-tolerance thickness of the radius (R) angle of structural components. The radius (R) is the fillet at the intersection of two surfaces of a structural component, including the outer fillet (positive R) and the inner fillet (negative R). Out-of-tolerance thickness of the radius (R) angle means that the measured thickness of the fillet of the structural component exceeds the design allowable range. For example... Figure 1 As shown, Figure 1 This is a cap-shaped girder cross-section, with an external radius (R1) and an internal radius (R2). Theoretically, the thickness of the external and internal radius (R2) of the cap-shaped girder should be consistent with the thickness of the planar region. However, due to the structural characteristics of the component, the actual pressure on the external radius (R2) region is greater than that on the planar region. Therefore, the actual thickness of the component gradually decreases as it transitions from the planar region to the external radius (R2), generally being thinnest at the external radius (R2). This manifests as an external radius (R2) thickness deviation, which is usually a thinning deviation and has a greater impact on the load-bearing capacity of the component. Therefore, how to adjust the external radius (R2) thickness deviation of the component has become a key research direction in the production of structural components in the aerospace field. Summary of the Invention

[0004] To address the aforementioned technical problems, this application aims to provide a resin composition, prepreg, preparation method, and structural component for interlayer dimension control structural components with excessive thickness at the convex radius corner. This resin composition can provide a toughening effect while increasing the flow resistance of the resin components in the convex radius corner region and reducing the sensitivity of the convex radius corner region to high pressure, thereby reducing the thickness deviation of the convex radius corner.

[0005] According to a first aspect of this application, a resin composition is provided for addressing excessive thickness tolerance in the external radius (R) corner of an interlayer dimension control structural component, the resin composition comprising the following raw materials by mass percentage: Resin matrix 55.7-72.3%; The first toughening agent is 12.7-30.3%; Second toughening agent: 8.2-18.4%; The resin matrix comprises a resin component and a curing agent, wherein the equivalent ratio of the active groups in the curing agent to the reactive groups in the resin component is 0.70-0.85. The solubility of the first toughening agent in the resin component is greater than or equal to a first preset threshold. The solubility of the second toughening agent in the resin component is less than or equal to a second preset threshold. The average particle size of the second toughening agent is 15-35 μm.

[0006] In some embodiments of this application, the mass ratio of the sum of the masses of the first toughening agent and the second toughening agent to the mass ratio of the resin component is 1:1.29-1.54.

[0007] In some embodiments of this application, the resin component includes one or more of the following: difunctional epoxy resin, trifunctional epoxy resin, and tetrafunctional epoxy resin. And / or, the curing agent includes amine curing agents; And / or, the first toughening agent comprises one or more of polysulfone, polyethersulfone, and polyphenylene ether; And / or, the second toughening agent comprises one or more of polyphthalamide, polyetherimide, and polyamide.

[0008] In some embodiments of this application, when the resin component includes a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional epoxy resin, the mass ratio of the difunctional epoxy resin, the trifunctional epoxy resin, and the tetrafunctional epoxy resin is 2.57-3.98:3.00-4.78:1.

[0009] According to a second aspect of this application, a prepreg is provided, the prepreg comprising a reinforcing fiber and a resin composition, wherein the reinforcing fiber comprises 60-70% of the mass of the prepreg; The resin composition includes the resin composition described above.

[0010] According to a third aspect of this application, a method for preparing a prepreg is provided, the method being used to prepare the prepreg as described above, the method comprising: A resin film is applied to both sides of the reinforcing fiber, and the reinforcing fiber is impregnated with the resin film under a first preset condition to obtain the prepreg. The resin film is formed by coating a resin composition.

[0011] In some embodiments of this application, the first preset condition includes: Temperature is 110-140℃, pressure is 200-800kg, and traction speed is 3-10m / min.

[0012] According to a fourth aspect of this application, a structural component is provided, which is formed by laying a predetermined amount of prepreg at a predetermined layup angle and then curing it under a second predetermined condition, wherein the prepreg includes the prepreg described above or a prepreg prepared by any of the methods described above.

[0013] In some embodiments of this application, the preset number is 9-25 layers.

[0014] In some embodiments of this application, the second preset condition includes: The temperature is 170-190℃, and the heat preservation time is 120-180 minutes.

[0015] The technical solution provided in this application may include the following beneficial effects: In this application, a first toughening agent is used as an intralayer toughening agent of the prepreg to provide a toughening effect, so that the structural component maintains good mechanical properties; a second toughening agent is used as an interlayer toughening particle of the prepreg, which, by utilizing its larger particle size and lower solubility in the resin component, makes it difficult for it to move between the layers of the prepreg, thereby increasing the flow resistance of the resin component in the convex corner region, reducing the sensitivity of the convex corner region to high pressure, and thus reducing the thickness deviation of the convex corner.

[0016] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] Figure 1 It is based on the schematic diagram of the cross-section of the hat-shaped stringer in the background art.

[0019] Figure 2 This is a schematic diagram of the cross-section of an eccentric R-angle that does not provide adequate support between layers.

[0020] Figure 3 This is a schematic diagram of the cross-section of an eccentric R-angle with good interlayer support. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0022] The convex radius (R-angle) of a cap-shaped stringer fabricated using conventional prepreg was cross-sectioned. The sectioned strips were then used to create metallographic cold-mounted specimens, which were subsequently ground and polished using an automated polishing machine. The internal structure of the convex radius of the cap-shaped stringer fabricated using conventional prepreg was observed under a metallographic microscope. Figure 2 and Figure 3 As shown, Figure 2 This is a schematic diagram of the cross-section of an external R-angle that does not provide adequate support between layers. Figure 3 This is a schematic diagram of a positive radius cross-section with good interlayer support. The spline consists of a fiber layer L1 and a resin layer L2. According to... Figure 2 It can be seen that the resin layer L2 is thinner in the positive R-corner area. From the positive R-corner to the planar area, the resin layer L2 gradually thickens and returns to the level of the planar area. This indicates that the excessive thickness of the positive R-corner is mainly related to the extrusion and loss of the resin layer L2 under high pressure.

[0023] Studies have shown that thickness deviations in external radius corners are generally due to thinning, and the main reasons include: 1. Uneven pressure transmission: This is caused by structural characteristics and is the root cause. Due to the curvature of the male mold's radius (R-zone), the pressure distribution varies, with the actual pressure at the male radius (R-angle) being greater than that in the planar area, resulting in a thinner thickness at the male radius (R-angle).

[0024] 2. Difference in resin flowability: Under the pressure difference caused by the structure of the R-zone of the male mold, the prepreg with higher resin flowability will have a greater degree of thinner R-angle thickness due to the easier occurrence of resin flow behavior.

[0025] To address the issue of out-of-tolerance thickness at external radius corners, the following methods can be used: 1. Auxiliary process measures: When the structural components are cured, a cover plate with a certain rigidity is used to control the loss of resin at the positive R corner through physical size restriction, so as to avoid the thickness from becoming thinner.

[0026] 2. Resin viscosity-temperature characteristics control: By adjusting the content of each component in the resin, the overall viscosity-temperature characteristics of the resin are controlled, thereby reducing the resin fluidity from the source.

[0027] The above methods can improve the problem of excessive thickness of the external radius corner to some extent, but the use of auxiliary process measures has structural limitations and will increase the difficulty and cost of the manufacturing process. It is difficult to simultaneously achieve the desired external radius corner thickness, prepreg performance, and manufacturability by controlling the viscosity-temperature characteristics of the resin alone.

[0028] Based on this, this application provides a resin composition comprising the following raw materials in weight percentages: 55.7-72.3% resin matrix; 12.7-30.3% first toughening agent; and 8.2-18.4% second toughening agent; wherein the resin matrix comprises a resin component and a curing agent, the equivalent ratio of active groups in the curing agent to reactive groups in the resin component is 0.70-0.85; the solubility of the first toughening agent in the resin component is greater than or equal to a first preset threshold; the solubility of the second toughening agent in the resin component is less than or equal to a second preset threshold; and the average particle size of the second toughening agent is 15-35 μm. In this application, a first toughening agent is used as an intralayer toughening agent of the prepreg to provide a toughening effect, so that the structural component maintains good mechanical properties; a second toughening agent is used as an interlayer toughening particle of the prepreg, which, by utilizing its larger particle size and lower solubility in the resin component, makes it difficult to move between the layers of the prepreg, thereby increasing the flow resistance of the resin component in the convex corner region, reducing the sensitivity of the convex corner region to high pressure, and thus reducing the thickness deviation of the convex corner.

[0029] The specific embodiments described below are intended to help those skilled in the art understand this embodiment, but this embodiment is not limited to the specific embodiments described below.

[0030] An exemplary embodiment of this application provides a resin composition for addressing excessive thickness tolerance at the external radius (R-angle) of an interlayer dimensional control structure. The resin composition comprises the following raw materials by mass percentage: Resin matrix 55.7-72.3%; The first toughening agent is 12.7-30.3%; Second toughening agent: 8.2-18.4%; The resin matrix includes resin components and a curing agent, wherein the equivalent ratio of active groups in the curing agent to reactive groups in the resin components is 0.70-0.85. The solubility of the first toughening agent in the resin component is greater than or equal to the first preset threshold. The solubility of the second toughening agent in the resin component is less than or equal to the second preset threshold. The average particle size of the second toughening agent is 15-35 μm.

[0031] In this embodiment, a first toughening agent is used as an intralayer toughening agent of the prepreg to provide a toughening effect, so that the structural component maintains good mechanical properties; a second toughening agent is used as an interlayer toughening particle of the prepreg, which, by utilizing its larger particle size and lower solubility in the resin component, makes it difficult to move between the layers of the prepreg, thereby increasing the flow resistance of the resin component in the convex corner region, reducing the sensitivity of the convex corner region to high pressure, and thus reducing the thickness deviation of the convex corner.

[0032] Among them, flow resistance refers to the ability to impede the flow of resin. By using a second toughening agent with a specific particle size, the flowability of the resin component in the positive R-corner region can be reduced, so that the resin component can uniformly impregnate the reinforcing fibers in the prepreg, thereby improving the thickness deviation of the positive R-corner of the molded structural part.

[0033] This application, through the synergistic effect of the first toughening agent and the second toughening agent, can adjust the problem of excessive thickness of the external R-corner of the structural component by controlling the micro-size of the interlayer of the prepreg without making excessive adjustments to the composition and content of the resin matrix.

[0034] The first preset threshold refers to the degree of solubility of the first toughening agent in the resin component at a preset preparation temperature. For example, if the first preset threshold is 90%, the solubility of the first toughening agent in the resin component is greater than 90%. Therefore, the solubility of the first toughening agent in the resin component can be 92%, 95%, or 100%, indicating that the first toughening agent has good solubility in the resin component at the preset preparation temperature. The particle size of the first toughening agent is not limited, as long as it can dissolve in the resin component. For example, the average particle size of the first toughening agent can be 15-100 μm. For instance, the average particle size of the first toughening agent can be 15 μm, 30 μm, 58 μm, 84 μm, or 100 μm.

[0035] The second preset threshold refers to the degree of solubility of the second toughening agent in the resin component at a preset preparation temperature. For example, if the second preset threshold is 10%, the solubility of the second toughening agent in the resin component is less than 10%. Therefore, the solubility of the second toughening agent in the resin component can be 0%, 3%, or 5%, indicating that the second toughening agent has poor solubility in the resin component at the preset preparation temperature and is difficult to dissolve in the resin component. The second toughening agent uses a larger particle size, resulting in lower flowability in the resin component, thereby increasing the flow resistance of the resin component in the anode corner region. Specifically, the average particle size of the second toughening agent needs to be controlled between 15-35 μm. If the average particle size is too small, it will be difficult to effectively increase the flow resistance of the resin component in the anode corner region; if the average particle size is too large, it will lead to excessive flow resistance in the anode corner region and will also affect the uniformity of resin component wetting of the reinforcing fiber. For example, the average particle size of the second toughening agent can be 15 μm, 20 μm, 28 μm, 30 μm, or 35 μm. The average particle size of the second toughening agent can also be any value between the exemplary average particle size values, for example, the average particle size of the second toughening agent can also be any value between 20-30 μm.

[0036] The resin matrix includes a resin component and a curing agent. The active groups in the curing agent react with the reactive groups in the resin component, causing the resin component to crosslink and cure. For example, when the curing agent is an amine-based curing agent, its active group is the active hydrogen atom on the amine group; when the resin component is an epoxy resin, the reactive group in the resin component is the epoxy group at the end of the epoxy resin molecule. The equivalence ratio is the ratio of the molar number of active hydrogen atoms in the curing agent to the molar number of epoxy groups in the epoxy resin. In this embodiment, when the equivalence ratio of the active groups in the curing agent to the reactive groups in the resin component is 0.70-0.85, the cured resin composition can simultaneously possess good mechanical strength and toughness. Exemplarily, the equivalence ratio of the active groups in the curing agent to the reactive groups in the resin component can be 0.70, 0.75, 0.78, 0.80, or 0.85. The equivalence ratio of the active matrix in the curing agent to the reactive groups in the resin component can also be any value between the exemplary equivalence ratios. For example, the equivalence ratio of the active groups in the curing agent to the reactive groups in the resin component can also be any value between 0.75 and 0.80.

[0037] In one embodiment, for example, the resin composition comprises raw materials in the following mass percentages: Resin matrix 55.7%; The first toughening agent was 30.3%; Second toughening agent 14.0%.

[0038] In another embodiment, the resin composition comprises the following raw materials in weight percentages: Resin matrix 60.0%; The first toughening agent is 24.5%; Second toughening agent 15.5%.

[0039] In another embodiment, the resin composition comprises the following raw materials in weight percentages: Resin matrix 64.0%; The first toughening agent was 22.0%; Second toughening agent 14.0%.

[0040] In another embodiment, the resin composition comprises the following raw materials in weight percentages: Resin matrix 68.0%; First toughening agent 20.0%; Second toughening agent 12.0%.

[0041] In another embodiment, the resin composition comprises the following raw materials in weight percentages: Resin matrix 55.7%; The first toughening agent was 25.9%; The second toughening agent is 18.4%.

[0042] In another embodiment, the resin composition comprises the following raw materials in weight percentages: Resin matrix 72.3%; The first toughening agent is 19.5%; The second toughening agent is 8.2%.

[0043] In another embodiment, the resin composition comprises the following raw materials in weight percentages: Resin matrix 72.3%; The first toughening agent was 12.7%; Second toughening agent 15.0%.

[0044] In an exemplary embodiment of this application, the mass ratio of the sum of the masses of the first toughening agent and the second toughening agent to the mass ratio of the resin component is 1:1.29-1.54.

[0045] In this embodiment, the mass ratio of the sum of the first and second toughening agents to the resin component is controlled at 1:1.29-1.54. This balances the strength, heat resistance, and toughness of the resin component while maintaining a suitable melt viscosity in the resin matrix, improving processability, and reducing thickness deviations in the convex radius corner. For example, the mass ratio of the sum of the first and second toughening agents to the resin component can be 1:1.29, 1:1.35, 1:1.38, 1:1.40, or 1:1.54. The mass ratio of the sum of the first and second toughening agents to the resin component can also be any of the exemplary mass ratios; for example, it can be any ratio between 1:1.35 and 1:1.40.

[0046] In an exemplary embodiment of this application, the resin component includes one or more of the following: difunctional epoxy resin, trifunctional epoxy resin, and tetrafunctional epoxy resin.

[0047] In this embodiment, the resin component can be one of a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional epoxy resin. Trifunctional and tetrafunctional epoxy resins can significantly improve the crosslinking density and heat resistance of the cured structural component. The lower viscosity of the difunctional epoxy resin can improve the wettability and processability of the resin component. The resin component can also be a mixture of multiple difunctional, trifunctional, and tetrafunctional epoxy resins to balance the mechanical and processability properties of the cured product. The epoxy equivalent of the difunctional epoxy resin can be 162-182 g / eq, the epoxy equivalent of the trifunctional epoxy resin can be 95-105 g / eq, and the epoxy equivalent of the tetrafunctional epoxy resin can be 117-134 g / eq. Among them, the difunctional epoxy resin includes bisphenol F type diglycidyl ether epoxy resin, the trifunctional epoxy resin includes acetaminophen trifunctional epoxy resin, and the tetrafunctional epoxy resin includes tetraglycidyl diaminodiphenylmethane epoxy resin.

[0048] In an exemplary embodiment of this application, the curing agent includes an amine curing agent.

[0049] In this embodiment, the curing agent can be an amine curing agent. The CN bonds formed by the reaction of the amine curing agent with the epoxy resin have good flexibility and impact resistance, while maintaining high tensile strength and flexural strength. Furthermore, the amine curing agent has good compatibility with the first toughening agent and the second toughening agent, which is beneficial for forming a dispersed phase structure, thereby improving the toughening effect of the cured structural component. The equivalent amount of the amine curing agent can be 60-64 g / eq. Exemplarily, the amine curing agent can be an aliphatic amine curing agent (e.g., diethylenetriamine, triethylenetetramine), alicyclic amine curing agent (e.g., isophorone diamine), aromatic amine curing agent (e.g., diaminodiphenylmethane, diaminodiphenyl sulfone), dicyandiamide, etc.

[0050] In an exemplary embodiment of this application, the first toughening agent includes one or more of polysulfone, polyethersulfone, and polyphenylene ether.

[0051] In this embodiment, the first toughening agent can be one of polysulfone, polyethersulfone, or polyphenylene ether. These materials have good compatibility with epoxy resin and can effectively improve the fracture toughness of the epoxy resin. The first toughening agent can also be multiple types of polysulfone, polyethersulfone, or polyphenylene ether. For example, the first toughening agent can be polysulfone and polyethersulfone in a mass ratio of 1.5-2.3:1.

[0052] In an exemplary embodiment of this application, the second toughening agent includes one or more of polyphthalamide, polyetherimide, and polyamide.

[0053] In this embodiment, the second toughening agent can be one of polyphthalamide, polyetherimide, and polyamide, which synergistically toughens with the first toughening agent to further improve the impact resistance of the cured structural component. Simultaneously, due to its low solubility in the resin component, it can form a dispersed phase that hinders the flow of the resin component, increasing the flow resistance of the resin component in the raised corner region, thereby reducing the thickness deviation of the raised corner. The second toughening agent can also be multiple of polyphthalamide, polyetherimide, and polyamide; for example, the second toughening agent can also be polyphthalamide and polyetherimide in a mass ratio of 1.0-1.5.

[0054] In an exemplary embodiment of this application, when the resin component includes difunctional epoxy resin, trifunctional epoxy resin, and tetrafunctional epoxy resin, the mass ratio of the difunctional epoxy resin, trifunctional epoxy resin, and tetrafunctional epoxy resin is 2.57-3.98:3.00-4.78:1.

[0055] In this embodiment, the resin components are compounded using difunctional, trifunctional, and tetrafunctional epoxy resins. The trifunctional epoxy resin constructs a highly cross-linked framework, while the difunctional resin controls processability and toughness, and the tetrafunctional epoxy resin controls heat resistance. This results in a cured structural component possessing excellent heat resistance, toughness, and processability. For example, the mass ratio of the difunctional, trifunctional, and tetrafunctional epoxy resins can be 2.57:3.00:1, 2.88:3.76:1, 3.25:4.12:1, 3.52:4.45:1, or 3.98:4.78:1. The mass ratio of difunctional epoxy resin, trifunctional epoxy resin and tetrafunctional epoxy resin can also be any ratio between exemplary mass ratios. For example, the mass ratio of difunctional epoxy resin, trifunctional epoxy resin and tetrafunctional epoxy resin can also be any ratio between 2.88-3.52:3.76-4.45:1.

[0056] An exemplary embodiment of this application provides a prepreg comprising reinforcing fibers and a resin composition, wherein the mass of the reinforcing fibers is 60-70% of the mass of the prepreg; and the resin composition comprises the resin composition of the above embodiment.

[0057] In this embodiment, a prepreg is formed by impregnating reinforcing fibers with a resin composition. The reinforcing fibers include one of carbon fiber, glass fiber, aramid fiber, and basalt fiber. Exemplarily, the reinforcing fibers can be, for example, unidirectional carbon fibers in 12K tow. The mass of the reinforcing fibers needs to be controlled at 60-70% of the prepreg mass. This ensures sufficient impregnation of the reinforcing fibers by the resin composition and excellent interfacial adhesion, while also providing good layup processability for the resulting prepreg, achieving a balance between mechanical properties and lightweighting. Exemplarily, the mass of the reinforcing fibers can be 60%, 63%, 67%, 69%, or 70% of the prepreg mass. The percentage of the reinforcing fibers to the prepreg mass can also be any value between the exemplary percentages; for example, the percentage of the reinforcing fibers to the prepreg mass can be any value between 63% and 69%.

[0058] An exemplary embodiment of this application provides a method for preparing a prepreg, the method being used to prepare the prepreg as described in the above embodiment, the method comprising: A resin film is coated on both sides of a reinforcing fiber, and the reinforcing fiber is impregnated with the resin film under a first preset condition to obtain a prepreg; wherein the resin film is coated with a resin composition.

[0059] In this embodiment, the resin film is coated on both sides of the reinforcing fiber, allowing for simultaneous and uniform wetting of the upper and lower surfaces of the reinforcing fiber, thereby reducing the porosity of the prepreg. The basis weight of the reinforcing fiber can be 190-200 g / m².2 The basis weight of the resin membrane can be 46-52 g / m³. 2 .

[0060] The resin composition can be prepared by the following method: The weighed resin components, first toughening agent, and second toughening agent are added to a resin reactor. The material is heated to 70-90℃, allowing the first and second toughening agents to pre-disperse in the resin components for 40-60 minutes. The dispersion disc speed is set to 300-500 rpm, and the agitator speed to 10-40 rpm. After pre-dispersion, the material is heated to 150-170℃, maintaining the dispersion disc speed at 300-500 rpm and the agitator speed at 10-40 rpm for 90-120 minutes to ensure uniform dispersion of the first and second toughening agents in the resin components. Then, the material is cooled to 60-85℃, and the weighed curing agent is added to the reactor. The dispersion disc speed is maintained at 100-150 rpm, and the agitator speed at 10-40 rpm for 30-60 minutes to obtain the resin composition.

[0061] Resin films can be made using the following methods: The resin composition is put into the resin tank of the coating machine, and the resin is coated at a metering roller temperature of 90-100℃ and a traction rate of 5-20m / min to obtain a resin film.

[0062] In an exemplary embodiment of this application, the first preset condition includes: Temperature is 110-140℃, pressure is 200-800kg, and traction speed is 3-10m / min.

[0063] In this embodiment, an impregnation machine can be used to impregnate the carbon fiber with a resin film under the conditions of a temperature of 110-140℃, a pressure of 200-800kg, and a traction speed of 3-10m / min, so as to obtain a prepreg with controlled interlayer micro-size.

[0064] For example, in one embodiment, the first preset conditions include: a temperature of 110°C, a pressure of 200 kg, and a traction speed of 3 m / min.

[0065] In another embodiment, the first preset conditions include: a temperature of 120°C, a pressure of 400 kg, and a traction speed of 5 m / min.

[0066] In another embodiment, the first preset conditions include: a temperature of 130°C, a pressure of 600 kg, and a traction speed of 7 m / min.

[0067] In another embodiment, the first preset conditions include: a temperature of 140°C, a pressure of 800 kg, and a traction speed of 10 m / min.

[0068] An exemplary embodiment of this application provides a structural component, which is formed by laying a preset amount of prepreg at a preset layup angle and then curing it under a second preset condition. The prepreg includes the prepreg described above or the prepreg prepared by the method of preparing the prepreg in any of the above embodiments.

[0069] In this embodiment, by laying a preset amount of prepreg according to a preset layup angle, and then curing it under a second preset condition, a structural component with mechanical properties and dimensional stability that meets the design requirements can be obtained. The preset layup angle can be, for example, ±45°, 0°, or 90°, and the layup needs to be symmetrical.

[0070] The preset number of layers can be 9-25 layers to ensure sufficient structural rigidity and manufacturing feasibility, while avoiding deformation problems caused by excessive thinness and curing defects and increased costs caused by excessive thickness. For example, the preset number of layers can be 10, 16, 20, or 24 layers.

[0071] In an exemplary embodiment of this application, the second preset condition includes: The temperature is 170-190℃, and the heat preservation time is 120-180 minutes.

[0072] In this embodiment, an autoclave curing method can be used to cure the prepreg after it has been laid. The temperature can be increased at a rate of 1-2 ℃ / min, which can ensure that the curing reaction is complete while avoiding defects such as internal delamination, cracking, and high porosity caused by excessive temperature difference, concentrated heat release, or stress accumulation, thereby obtaining a dense, uniform, and low-stress structural component.

[0073] For example, in one embodiment, the second preset conditions include: a temperature of 170°C and a heat preservation time of 120 minutes.

[0074] In another embodiment, the second preset conditions include: a temperature of 175°C and a heat preservation time of 130 minutes.

[0075] In another embodiment, the second preset conditions include: a temperature of 182°C and a heat preservation time of 150 minutes.

[0076] In another embodiment, the second preset conditions include: a temperature of 190°C and a heat preservation time of 180 minutes.

[0077] In this application, the structural component can be, for example, a cap-shaped stringer. Cap-shaped stringers are a common reinforcing structural component in aircraft fuselage and wing panels. Compared to stringers of other shapes, cap-shaped stringers, due to their excellent buckling resistance, are particularly suitable for large-size, high-load-bearing composite material panels, and are one of the key components for achieving lightweight and high-performance aircraft. However, because cap-shaped stringers have a closed deep cavity section, the prepreg in its convex corner region is under tension under pressure. After the resin component's viscosity decreases due to heat, it easily flows and migrates outward, resulting in localized insufficient resin component. Furthermore, because this region is located deep within the cavity, external pressure is difficult to effectively transmit, failing to compensate for the thickness loss caused by resin runoff. Therefore, conventional structural components are prone to thinning or uneven distribution at the convex corner, resulting in thickness deviations. This application, through the synergistic effect of the first and second toughening agents, can adjust the thickness deviation problem at the convex corner of the structural component by controlling the micro-sizes between the prepreg layers without excessively adjusting the composition and content of the resin matrix.

[0078] To more clearly explain the technical solution of this application, specific embodiments of the resin composition are provided. The beneficial effects of selecting the above-mentioned range of component content will be explained by providing specific experimental data through specific embodiments.

[0079] Example It should be noted that, unless otherwise specified, the raw materials used in the following examples are all commercially available. The first toughening agent is polyethersulfone, and the second toughening agent is polyamide, both with an average particle size of 20 μm. The curing agent is sulfamic acid curing agent.

[0080] Example 1: A method for preparing a resin composition, comprising the following steps: The resin component, first toughening agent, and second toughening agent were added to a resin reactor. The material was heated to 90°C to pre-disperse the first and second toughening agents in the resin component for 60 minutes, with the dispersion disc speed set to 500 rpm and the agitator speed to 40 rpm. After pre-dispersion, the material was heated to 150-170°C, maintaining the dispersion disc speed at 500 rpm and the agitator speed at 40 rpm for 120 minutes to ensure uniform dispersion of the first and second toughening agents in the resin component. The material was then cooled to 85°C, and the curing agent was added to the reactor. The dispersion disc speed was maintained at 150 rpm and the agitator speed at 40 rpm for 60 minutes to obtain the resin composition. In this resin composition, the resin matrix comprises 65.0% by mass (e.g., 65.0 kg), the first toughening agent comprises 25.0% by mass (e.g., 25.0 kg), and the second toughening agent comprises 10.0% by mass (e.g., 10.0 kg). The resin matrix consists of resin components and a curing agent. The resin components include bisphenol F type diglycidyl ether epoxy resin and acetaminophen trifunctional epoxy resin in a mass ratio of 3.33:4.00:1. Resin, tetraglycidyl diaminodiphenylmethane epoxy resin; the equivalent ratio of the active group of the curing agent to the reactive group in the resin component is 0.75 (for example, the amount of resin component is 47.22 kg, the amount of bisphenol F type diglycidyl ether epoxy resin is 14.17 kg, the amount of acetaminophen trifunctional epoxy resin is 17.02 kg, the amount of tetraglycidyl diaminodiphenylmethane epoxy resin is 4.25 kg, and the amount of curing agent is 17.78 kg).

[0081] To more clearly explain the technical solution of this application, this application also provides examples 2-10 of resin compositions, wherein the ingredients of examples 2-10 are shown in Table 1.

[0082] Table 1 shows specific examples of the resin compositions used in this application. It should be noted that, except for the parameters listed in Table 1, the other parameters of Examples 2-10 are basically the same as those of Example 1.

[0083] In Table 1, the ratio C1 represents the mass ratio of difunctional epoxy resin, trifunctional epoxy resin, and tetrafunctional epoxy resin.

[0084] The ratio C2 is the sum of the masses of the first toughening agent and the second toughening agent, and the mass ratio of the resin component.

[0085] Table 1. Ingredients of the resin compositions in the examples (unit: %)

[0086] Comparative example: Comparative Example 1: The main difference between this comparative example and Example 1 is that the average particle size of the second toughening agent is 10 μm.

[0087] Comparative Example 2: The main difference between this comparative example and Example 1 is that the average particle size of the second toughening agent is 10 μm, and the mass percentage of the second toughening agent is 15.0%, while the mass percentage of the resin matrix is ​​60.0%.

[0088] Application examples The resin compositions in the examples were used to prepare prepregs, and the prepregs were cured and molded to obtain structural components of cap-shaped stringers. Examples 1-10 correspond to the resin compositions of Examples 1-10, respectively.

[0089] (1) The resin composition is put into the resin tank of the coating machine, and the resin is coated at a metering roller temperature of 90°C and a traction speed of 10 m / min to obtain a resin film; the basis weight of the resin film is 50 g / m 2 .

[0090] (2) The resin film is coated on both sides of the reinforcing fiber, and the resin film is used to impregnate the reinforcing fiber under the first preset condition to obtain a prepreg. The reinforcing fiber is a unidirectional carbon fiber with a 12K tow and a basis weight of 194 g / m². 2 The first preset conditions are: temperature 120℃, pressure 800kg, and traction speed 5m / min.

[0091] (3) The prepreg is laid in 9 layers of cap-shaped stringers at an angle of 45° / 0° / 0° / -45° / 90° / -45° / 0° / 0° / 0° / 45°. The cap-shaped stringers are cured in an autoclave at a heating rate of 2℃ / min, a holding temperature of 180℃, and a holding time of 120min to form a structural component.

[0092] Comparison Example Comparative Example 1: The main difference between this comparative example and application example 1 is that the resin composition of comparative example 1 is used.

[0093] Comparative Example 2: The main difference between this comparative example and application example 1 is that the resin composition of comparative example 2 is used.

[0094] Performance testing The performance of the prepreg and structural components for the corresponding use cases and control cases were tested according to the following methods, and the test results are shown in Table 2.

[0095] 1. Impregnation and water absorption: The impregnation of prepregs was tested using the standard test method of ASTM D8132 / D8132M-17, which measures the permeability of the prepregs.

[0096] 2. Qualitative evaluation of prepreg tackiness: In a temperature and humidity environment of 22±1℃ and 55±10%RH, two pieces of prepreg are naturally stacked and left to stand for 1 minute. If the two pieces of prepreg can be quickly and without damage separated, the tackiness is moderate. If careful handling is required for separation without damage, the tackiness is slightly tacky. If separation without damage is not possible (the prepreg must be damaged to separate), the tackiness is sticky.

[0097] 3. Percentage of thickness deviation at the external radius (R-angle): The thickness of the external radius (R-angle) and planar area of ​​the cured cap-shaped stringer structural component is measured using a magnetic thickness gauge and compared with the theoretical thickness to calculate the percentage of thickness deviation.

[0098] 4. Metallographic Interlayer Resin Condition at the Exposed Radius Corner: The cross-section of the exposed radius corner of the cap-shaped stringer, obtained through thickness measurement, was sectioned. The sectioned strip was then used to create metallographic cold-mounted specimens, which were then ground and polished using an automatic polishing machine. Under a metallographic microscope, the interlayer resin thickness of the stringer structure was measured at both the exposed radius corner and the flat plate area. If (flat plate area resin thickness - exposed radius corner resin thickness) / flat plate area resin thickness was less than or equal to 10%, the exposed radius corner had a higher interlayer resin content; if it was greater than 10%, the exposed radius corner had a lower interlayer resin content.

[0099] Table 2 Performance Test Tables for Structural Components in Application Examples and Comparison Examples

[0100] Combining the data in Tables 1 and 2, it can be seen that when the average particle size of the second toughening agent in Comparative Example 1 is small, the prepreg's viscosity qualitative evaluation is "viscous," indicating poor processability. In Example 1, when the average particle size of the second toughening agent is 20 μm, the prepreg's viscosity qualitative evaluation is "moderate," indicating good processability. Therefore, it can be concluded that structural components using a larger particle size second toughening agent have smaller deviations in the thickness of the external R-angle and more significant support for the interlayer resin. However, even after increasing the content of the ordinary particle size (10 μm) second toughening agent to 15%, the thickness deviation of the external R-angle still does not reach the level of a 10% content large particle size second toughening agent.

[0101] Therefore, by using a second toughening agent with large particle size for interlayer toughening, this application can play a role in micro-dimensional control of the interlayer of prepreg while ensuring good manufacturability and processability, thereby obtaining a smaller deviation in the thickness of the positive R-angle of the molded structural part.

[0102] Furthermore, it can be seen from Examples 1-10 and Application Examples 1-10 that Examples 6-8 have better performance, indicating that by further optimizing the mass ratio of difunctional epoxy resin, trifunctional epoxy resin and tetrafunctional epoxy resin in the resin composition, the thickness deviation of the positive R corner of the prepreg can be further improved.

[0103] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0104] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A resin composition for a structural component with excessive thickness tolerance at the external radius (R-angle), characterized in that, The resin composition comprises the following raw materials in the indicated weight percentages: Resin matrix 55.7-72.3%; The first toughening agent is 12.7-30.3%; Second toughening agent: 8.2-18.4%; The resin matrix comprises a resin component and a curing agent, wherein the equivalent ratio of the active groups in the curing agent to the reactive groups in the resin component is 0.70-0.

85. The solubility of the first toughening agent in the resin component is greater than or equal to a first preset threshold. The solubility of the second toughening agent in the resin component is less than or equal to a second preset threshold. The average particle size of the second toughening agent is 15-35 μm.

2. The resin composition for the excessive thickness of the external R-angle of the interlayer dimension control structure according to claim 1, characterized in that, The mass ratio of the sum of the first toughening agent and the second toughening agent to the mass of the resin component is 1:1.29-1.

54.

3. The resin composition for the excessive thickness of the external R-angle of the interlayer dimension control structure according to claim 1, characterized in that, The resin component includes one or more of the following: difunctional epoxy resin, trifunctional epoxy resin, and tetrafunctional epoxy resin; And / or, the curing agent includes amine curing agents; And / or, the first toughening agent comprises one or more of polysulfone, polyethersulfone, and polyphenylene ether; And / or, the second toughening agent comprises one or more of polyphthalamide, polyetherimide, and polyamide.

4. The resin composition for the excessive thickness of the external R-angle of the interlayer dimension control structure according to claim 3, characterized in that, When the resin component includes difunctional epoxy resin, trifunctional epoxy resin, and tetrafunctional epoxy resin, the mass ratio of the difunctional epoxy resin, the trifunctional epoxy resin, and the tetrafunctional epoxy resin is 2.57-3.98:3.00-4.78:

1.

5. A prepreg, characterized in that, The prepreg comprises a composition of reinforcing fibers and resin, wherein the mass of the reinforcing fibers is 60-70% of the mass of the prepreg; The resin composition includes the resin composition of the interlayer dimension control structure with excessive thickness tolerance at the convex R-angle as described in any one of claims 1-4.

6. A method for preparing a prepreg, characterized in that, The preparation method is used to prepare the prepreg as described in claim 5, and the preparation method includes: A resin film is applied to both sides of the reinforcing fiber, and the reinforcing fiber is impregnated with the resin film under a first preset condition to obtain the prepreg. The resin film is formed by coating a resin composition.

7. The method for preparing the prepreg according to claim 6, characterized in that, The first preset conditions include: Temperature is 110-140℃, pressure is 200-800kg, and traction speed is 3-10m / min.

8. A structural component, characterized in that, The structural component is formed by laying a preset amount of prepreg at a preset layup angle and then curing it under a second preset condition. The prepreg includes the prepreg as described in claim 5 or the prepreg prepared by the method described in any one of claims 6-7.

9. The structural component according to claim 8, characterized in that, The preset number is 9-25 layers.

10. The structural component according to claim 8, characterized in that, The second preset condition includes: The temperature is 170-190℃, and the heat preservation time is 120-180 minutes.

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